I've always taken my health for granted. I smoked my way through my 20s, smugly assuming I was immune to harm. The one chink in my family's genetic armor was my paternal grandmother, Edith, who, though she lived to be 90, had multiple bouts with cancer. Her first, uterine, was diagnosed at 47, followed by two battles with colon cancer in her 70s and 80s. Because of this, my father, Howie, had regular colonoscopies. When one of them turned up precancerous polyps, he urged me and my sister, Alison, who's 15 months older than I, to get screened when we turned 40. I knew I should do it, but the birthday came and went and I kept putting off the unpleasant test.

Then, last May, in a fit of physical housekeeping, I made a slew of doctor's appointments, including one for my first colonoscopy. When I woke up afterward, at Long Island College Hospital in Brooklyn, New York, my gastroenterologist, Irwin Grosman, M.D., greeted me formally, as if he hadn't just probed my insides. "I removed a 3-centimeter polyp from your sigmoid colon," he said. My mother, who was there to help me get home, asked, "Do you think it looked like a tumor?"

I'd never heard of Lynch syndrome. When I Googled it, I learned that it is an inherited genetic mutation that increases one's risk for cancers of the colon, uterus, ovaries, bladder, ureter and, rarely, the brain, among others. If I had it, my lifetime chance for colon cancer would be up to 85 percent (versus 5 percent for most women); for uterine cancer, my risk would be up to 60 percent (versus less than 3 percent). Bad odds, indeed.

Still, I didn't panic. For one thing, Lynch syndrome is rare: It's linked to only 5 percent of colon cancers. I was even calm the next day, when I went in for a Pap smear and hysteroscopy. As the doctor inserted the scope, I watched images from my uterus appear on a monitor. "What's that?" I asked, pointing to what looked like a flesh-colored stalactite. "Good eye—that's a polyp," my doctor said. "Wow! There's a whole nest of them!" I wondered if anyone had ever fainted with a camera in her vagina before. The doctor advised me to have my uterus scraped clean, which I did a few days later. The lab results from my colon and uterus would arrive around the same time.

Friends urged me to be optimistic, but I was more used to bad news when it came to cancer test results. My first husband, Glenn, had died of lung cancer nine years earlier, at only 34. A nonsmoker, his diagnosis was described as a fluke—ice-cold comfort. His death was swift. At 35, I was left a widow with two daughters: Maggie, a kindergartner, and Lucy, a toddler.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

Now here I was again, awaiting the worst. Usually, I tend to laugh off negative emotions. This time, my jokes fell flat. If I had cancer, I vowed to be realistic about it. Glenn had chosen denial, refusing to discuss his (bleak) odds for survival. I appreciated the allure of his approach but didn't think it would serve me. Instead, I resolved to bravely face whatever lay ahead.

The news, when it came, was mixed. The uterine polyps were benign. The colon polyp was a tubulovillous adenoma with high-grade dysplasia and foci of intramucosal carcinoma. Meaning stage 0 colon cancer. "We also found markers for Lynch syndrome," Dr. Grosman said. Lynch was all but confirmed.

With this turn of events, I could look forward to annual screenings of various body parts, although my uterus and ovaries couldn't be reliably scoped, he explained. Because cancer in these organs is usually discovered at later stages, it tends to be particularly deadly. "Most experts suggest that women with Lynch syndrome have prophylactic hysterectomies at 40, or whenever they've finished having kids," Dr. Grosman said. At 44, my female parts were four years past their expiration date.

My sister's colonoscopy also turned up a polyp, with precancerous cells. Like father, like daughters. Almost overnight, our clan had gone from seemingly robust to…what? Was I basically healthy, as I'd assumed, or ill? Should I be grateful for the scientific advances that had given me forewarning? Unlike my older, deader relatives, at least I could take preventive measures.

Every family has some bad genes. Yet being cancer-prone seemed worse to me than a family trait for heart disease. There are medications to lower cholesterol; there is no drug to prevent colon cancer. Suddenly, my dad, sister and I were in limbo, teetering between sick and well. Together, with my mom in tow, we decided to talk to the experts at Memorial Sloan-Kettering Cancer Center in New York City and made an appointment for several months hence.

When the day came, I sat listening to all the ways I could die. First, Yelena Kemel, a genetics counselor at MSK, showed us a chart of our family tree, based on research we'd done of our kin's maladies. On Dad's side, there was a great uncle with pancreatic cancer; two more relatives with colon and bladder, respectively; and Edith, with her colon cancers, plus a uterine and a ureteral. On Mom's side, there was breast (perhaps the one organ not related to Lynch) but no colon cancer.

Next, the oncologist swept in and issued the hospital's standard Lynch syndrome recommendations. The suggestion for my father: annual colonoscopies, endoscopies every four years, plus urine and renal screenings. For Alison and me: the same standard screening recommendations, as well as removal of our ovaries, uterus, fallopian tubes and cervix.

By now, I'd had some time to get used to this idea. I figured, leave me my vagina and clitoris (especially the latter) and I'd get by. Then I heard the recommendation for me, and me alone: a total colectomy, or removal of my colon. He wanted me to have my guts cut out. "What?!"

"The only way to make sure that you never get colon cancer again is to remove the organ," he explained.

I felt numb. "Why can't I just get screenings?" I asked.

"That's not a guarantee," he said. Because Lynch polyps tend to grow rapidly, one missed polyp could have dire consequences.

I was relatively young, and I could run 8 miles. And yet, a doctor had just announced that if I didn't have nearly every organ below my waist scooped out, I might die.

When I got home, I tried to joke about it with my husband, Steve, in my typical fashion. "Hey, without any internal organs, I might finally have a waist...." But soon enough, melancholy set in. No reputable doctor would tell a person to have herself eviscerated unless he believed it was truly necessary.

But was I in imminent danger? Despite four bouts with cancer, my grandmother Edith had lived to be 90. The odds were that I'd get cancer again, yes. But I could be treated, couldn't I? "It's a question of how much risk you can tolerate," Dr. Grosman told me when I consulted him again. When I called Kemel for more hard numbers, she gave them to me: "There's a 50 to 70 percent chance that your colon cancer will recur, and an 80 to 90 percent chance of preventing it by early detection."

I was looking for a reason to avoid surgery, so it was easy to take those odds and decide to keep my colon. Apparently, I have a relatively high tolerance for risk. But I couldn't avoid a hysterectomy. "Annual screenings don't appear to reduce gynecological cancer mortality in women with Lynch syndrome," Kemel had explained. I booked my surgery for a few months later.

Choosing not to have a colectomy could be the worst decision I've ever made. Both Maggie and Lucy, now ages 15 and 11, still recalled Glenn's illness and death. It would be cruel to put them through that again with their mother. When I imagined the possibility of me getting sick, of going through chemo, of possibly dying, I practically doubled over with grief. And with guilt.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

Then I thought about Steve: He wasn't the most organized guy. If I got cancer, would he be able to keep track of medications? Not at all aggressive, would he demand answers from cryptic doctors? My doubt grew—kind of like a tumor—until one night, at 3 a.m. (the bitching hour), I shook Steve awake and asked, "Are you going to get on the phone and fight with my insurance company over every bill they refuse to pay?"

Not fully awake, Steve said, "Whaaa?"

"What if I'm too weak to feed myself?" I said.

Alert now, he looked hurt. "I'll do whatever needs doing!"

I flashed to Lucy's last stomach bug, when Steve had done all the cleaning up. When Maggie had pneumonia, he'd nursed her back to health. He had been tested and had proved himself.

"You're not afraid I won't care for you," he said. "You hate the idea of being vulnerable, or relying on someone else, even me."

With shame, I realized that I'd twisted my fear into doubt of the man who loved me most. "You're right. I'm an idiot."

My new reality: living with the very real threat of cancer and the guilt of not doing everything possible to prevent it. Would I rather turn back time to before I'd heard of Lynch syndrome? No. I'd rather know the truth, because one day, there might be a therapy to correct it. Forearmed, I can make sure my daughters, who have a 50 percent chance of inheriting the mutation themselves, are first in line for treatment.

I've always taken my independence for granted. But I've gradually discovered, in this year of discoveries, that I can derive even greater power by letting myself feel secure in the certainty that my family will care for me as well as I have cared for them.

I had my hysterectomy in May. Watching Steve handle everything, I fell in love with him all over again. I hope I live until 90, like my grandma Edith, but if I don't, my daughters won't be alone. It comforts me to know that Maggie and Lucy will have Steve, and the three of them will have each other.